Lewandowski Kathryn E, Ongür Dost, Sperry Sarah H, Cohen Bruce M, Sehovic Selma, Goldbach Jacqueline R, Du Fei
1] McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA [2] McLean Hospital, Harvard Medical School, Boston, MA, USA.
McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA.
Neuropsychopharmacology. 2015 Mar 13;40(5):1243-9. doi: 10.1038/npp.2014.310.
White matter (WM) abnormalities are among the most commonly reported neuroimaging findings in bipolar disorder. Nonetheless, the specific nature and pathophysiology of these abnormalities remain unclear. Use of a combination of magnetization transfer ratio (MTR) and diffusion tensor spectroscopy (DTS) permits examination of myelin and axon abnormalities separately. We aimed to examine myelination and axon geometry in euthymic patients with bipolar disorder with psychosis (BDP) by combining these two complementary noninvasive MRI techniques. We applied a combined MRI approach using MTR to study myelin content and DTS to study metabolite (N-acetylaspartate, NAA) diffusion within axons in patients with BDP (n=21) and healthy controls (n=24). Data were collected from a 1 × 3 × 3-cm voxel within the right prefrontal cortex WM at 4 Tesla. Clinical and cognitive data were examined in association with MTR and DTS data. MTR was significantly reduced in BDP, suggesting reduced myelin content. The apparent diffusion coefficient of NAA did not differ from healthy controls, suggesting no changes in axon geometry in patients with BDP. These findings suggest that patients with BDP exhibit reduced myelin content, but no changes in axon geometry compared with controls. These findings are in contrast with our recent findings, using the same techniques, in patients with schizophrenia (SZ), which suggest both myelination and axon abnormalities in SZ. This difference may indicate that alterations in WM in BDP may have unique causes and may be less extensive than WM abnormalities seen in SZ.
白质（WM）异常是双相情感障碍中最常报告的神经影像学发现之一。尽管如此，这些异常的具体性质和病理生理学仍不清楚。联合使用磁化传递率（MTR）和扩散张量光谱（DTS）可以分别检查髓鞘和轴突异常。我们旨在通过结合这两种互补的非侵入性MRI技术，检查伴有精神病性症状的双相情感障碍（BDP）缓解期患者的髓鞘形成和轴突几何结构。我们应用联合MRI方法，使用MTR研究髓鞘含量，使用DTS研究BDP患者（n = 21）和健康对照者（n = 24）轴突内代谢物（N - 乙酰天门冬氨酸，NAA）的扩散。在4特斯拉磁场下，从右侧前额叶皮质白质内一个1×3×3厘米的体素中收集数据。将临床和认知数据与MTR和DTS数据相关联进行检查。BDP患者的MTR显著降低，表明髓鞘含量减少。NAA的表观扩散系数与健康对照者无差异，表明BDP患者的轴突几何结构无变化。这些发现表明，与对照组相比，BDP患者的髓鞘含量减少，但轴突几何结构无变化。这些发现与我们最近使用相同技术在精神分裂症（SZ）患者中的发现形成对比，后者表明SZ患者存在髓鞘形成和轴突异常。这种差异可能表明，BDP患者白质的改变可能有独特的原因，且可能不如SZ患者的白质异常广泛。
